1. Field of the Invention
Embodiments of the present invention relate to a stack package, and more particularly to a technology capable of easily selecting a specific chip in a chip stack package formed of stacked Through Silicon Vias (TSVs).
2. Related Art
In recent times, the demand of super-miniaturized and high-capacity semiconductor memories is rapidly increasing in response to a miniaturization and a higher-performance of electronic appliances and the increasing demand of mobile products. Generally, a variety of methods for increasing storage capacity of semiconductor memories have been widely used. First, one method for increasing storage capacity of semiconductor memories is to increase the integration degree of semiconductor chips. Second, another method for increasing storage capacity of semiconductor memories is to populate and assemble a plurality of semiconductor chips into a single semiconductor package.
The method of increasing storage capacity of semiconductor memories requires much more efforts and costs and much longer time. However, the method of increasing the integration degree of semiconductor chips is able to easily increase storage capacity of semiconductor memories by changing only the packaging method.
In addition, the method of increasing the integration degree of semiconductor chips is more advantageous than the method of increasing storage capacity of semiconductor memories in terms of costs, efforts, and time consumed in development and research environments. As a result, manufacturers of semiconductor memories have made efforts to increase storage capacity of semiconductor memory devices through multi-chip packaging in which multiple semiconductor chips are populated on a single semiconductor package.
For example, in order to populate a plurality of semiconductor chips into a single semiconductor package, a method for horizontally populating a semiconductor chip and a method for vertically populating a semiconductor chip into a single semiconductor package may be used. However, due to the pursuit of miniaturization of electronic appliances, most semiconductor memory manufacturers prefer to use Stack Type Multi Chip Packaging in which multiple semiconductor chips are vertically stacked and packaged. A representative example of such stack packages is to use packaging based on Through Silicon Via (TSV).
FIG. 1 is a perspective view illustrating a conventional stack package according to the related art. FIG. 2 is a cross-sectional view illustrating a specific part (i.e., a chip-selection pad part) of FIG. 1. FIG. 3 is a diagram illustrating a connection of a chip-selection pad through redistribution layers.
The conventional stack package shown in FIG. 1 is formed by stacking semiconductor chips (20, 30, 40, 50) on a substrate 10. The semiconductor chips (20, 30, 40, 50) are connected to TSVs (24, 34, 44, 54) as shown in FIG. 2.
A power-supply voltage VCC, a pad 12, a ground voltage VSS, and a pad 14 are present on the substrate 10. In addition, various I/O pads are present in each of the semiconductor chips (20, 30, 40, 50), and some pads are used as chip-selection pads (22, 32, 42, 52) for chip selection.
When the same chip is stacked with TSVs (24, 34, 44, 54), the chip-selection pads (22, 32, 42, 52) are located at the same position, such that it is impossible to perform chip selection using the same TSVs. Therefore, redistribution layers (26, 36, 46, 56) shown in FIG. 3 are formed on chip selection pads (22, 32, 42, 52), respectively, and need to be coupled to TSVs (28, 38, 48, 58) illustrated in FIG. 3 that may be located at different positions.
However, the above-mentioned method unavoidably increases fabrication costs and many fabrication management problems because retribution layers of stacked chips have different patterns. In addition, as many chip-selection pads (22, 32, 42, 52) as the number of stacked semiconductor chips (20, 30, 40, 50) need to be allocated. Therefore, when stacking the semiconductor chips, the number of chip selection pads increases such that the size of a stack package also increases.